i think the advice about certain places being 'better' than others can apply on a fairly benign weather day or sometimes after heavy rain (clearly Central/TST/Kwun Tong etc will be heavy in roadside pollution most days) but when we get things like inversion, pushing all the particulate crap down into a blanket covering HK from shore to shore, with the accompanying red sunset at 4pm, it doesn't matter where you are...in other words, OP, consider the advice as a 'best case scenario' only, but don't expect sparkling clean air in any particular place here...